// re2d $INPUT -o $OUTPUT -ci
module main;

enum ERROR = ulong.max;
/*!conditions:re2c*/

private void add(ulong BASE)(ref ulong u, int d) {
    u = u * BASE + d;
    if (u > uint.max) { u = ERROR; }
}

private ulong parse_u32(const(char)* s) {
    const(char)* yycursor = s, yymarker;
    YYCond c = YYCond.yycinit;
    ulong u = 0;

    /*!re2c
        re2c:yyfill:enable = 0;
        re2c:define:YYCTYPE = char;
        re2c:define:YYGETCOND = "c";
        re2c:define:YYSETCOND = "c = @@;";

        <*> * { return ERROR; }
        <init> '0b' / [01]        :=> bin
        <init> "0"                :=> oct
        <init> "" / [1-9]         :=> dec
        <init> '0x' / [0-9a-fA-F] :=> hex
        <bin, oct, dec, hex> "\x00" { return u; }
        <bin> [01]  { add!(2)(u,  yycursor[-1] - '0');      goto yyc_bin; }
        <oct> [0-7] { add!(8)(u,  yycursor[-1] - '0');      goto yyc_oct; }
        <dec> [0-9] { add!(10)(u, yycursor[-1] - '0');      goto yyc_dec; }
        <hex> [0-9] { add!(16)(u, yycursor[-1] - '0');      goto yyc_hex; }
        <hex> [a-f] { add!(16)(u, yycursor[-1] - 'a' + 10); goto yyc_hex; }
        <hex> [A-F] { add!(16)(u, yycursor[-1] - 'A' + 10); goto yyc_hex; }
    */
}



void main() {
    assert(parse_u32("") == ERROR);
    assert(parse_u32("1234567890") == 1234567890);
    assert(parse_u32("0b1101") == 13);
    assert(parse_u32("0x7Fe") == 2046);
    assert(parse_u32("0644") == 420);
    assert(parse_u32("9999999999") == ERROR);
}
